Massive digester rework.

This moves actual digest creation and sending into a new queue runner.  That
way, digest creation does not block the main incoming processor.  Lots of code
clean up and reorganization too, and many fixes.

digest_last_sent_at: Make this a DateTime
digest_size_threshold: Make this a Float
digest_volume_frequency: Make this an Enum

DigestFrequency: new enum

Fix up IMailingList interface to reflect reality.

In Runner base class, allow for msg.get_sender() to return a False value.  If
this happens (as it can with the empty marker messages used to signal the
digester that there's work to do), just use the list's preferred language.

Give the retry.py and incoming.py queue runner modules some proper epilogues.

The EmptyingRunner (for testing) logs itself as the runner its wrapping.

The digest file name now ends in .mmdf since that's the format we're using.

Add 'create_list' to doctest globals.

Add a Mailbox class to add support for the context manager protocol.

2 files changed, 118 insertions, 859 deletions

diff --git a/src/mailman/pipeline/docs/digests.txt b/src/mailman/pipeline/docs/digests.txt
index cb939f7ca..6aafef62c 100644
--- a/src/mailman/pipeline/docs/digests.txt
+++ b/src/mailman/pipeline/docs/digests.txt
@@ -6,13 +6,7 @@ as individual messages when immediately posted.  There are several forms of
 digests, although only two are currently supported: MIME digests and RFC 1153
 (a.k.a. plain text) digests.
 
-    >>> from mailman.pipeline.to_digest import process
-    >>> mlist = config.db.list_manager.create(u'_xtest@example.com')
-    >>> mlist.preferred_language = u'en'
-    >>> mlist.real_name = u'XTest'
-    >>> mlist.subject_prefix = u'[_XTest] '
-    >>> mlist.one_last_digest = set()
-    >>> switchboard = config.switchboards['virgin']
+    >>> mlist = create_list('xtest@example.com')
 
 This is a helper function used to iterate through all the accumulated digest
 messages, in the order in which they were posted.  This makes it easier to
@@ -21,515 +15,97 @@ update the tests when we switch to a different mailbox format.
     >>> from mailman.testing.helpers import digest_mbox
     >>> from itertools import count
     >>> from string import Template
-    >>> def makemsg():
+
+    >>> def message_factory():
     ...     for i in count(1):
     ...         text = Template("""\
     ... From: aperson@example.com
-    ... To: _xtest@example.com
+    ... To: xtest@example.com
     ... Subject: Test message $i
     ...
     ... Here is message $i
     ... """).substitute(i=i)
     ...         yield message_from_string(text)
+    >>> message_factory = message_factory()
 
 
 Short circuiting
 ----------------
 
 When a message is posted to the mailing list, it is generally added to a
-running collection of messages.  For now, this is a Unix mailbox file,
-although in the future this may end up being converted to a maildir style
-mailbox.  In any event, there are several factors that would bypass the
-storing of posted messages to the mailbox.  For example, the mailing list may
-not allow digests...
+mailbox, unless the mailing list does not allow digests.
 
     >>> mlist.digestable = False
-    >>> msg = makemsg().next()
+    >>> msg = next(message_factory)
+    >>> process = config.handlers['to-digest'].process
     >>> process(mlist, msg, {})
-    >>> sum(1 for mboxmsg in digest_mbox(mlist))
+    >>> sum(1 for msg in digest_mbox(mlist))
     0
-    >>> switchboard.files
+    >>> digest_queue = config.switchboards['digest']
+    >>> digest_queue.files
     []
 
 ...or they may allow digests but the message is already a digest.
 
     >>> mlist.digestable = True
     >>> process(mlist, msg, dict(isdigest=True))
-    >>> sum(1 for mboxmsg in digest_mbox(mlist))
+    >>> sum(1 for msg in digest_mbox(mlist))
     0
-    >>> switchboard.files
+    >>> digest_queue.files
     []
 
 
 Sending a digest
 ----------------
 
-For messages which are not digests, but which are posted to a digestable
+For messages which are not digests, but which are posted to a digesting
 mailing list, the messages will be stored until they reach a criteria
 triggering the sending of the digest.  If none of those criteria are met, then
 the message will just sit in the mailbox for a while.
 
     >>> mlist.digest_size_threshold = 10000
     >>> process(mlist, msg, {})
-    >>> switchboard.files
+    >>> digest_queue.files
     []
     >>> digest = digest_mbox(mlist)
-    >>> sum(1 for mboxmsg in digest)
+    >>> sum(1 for msg in digest)
     1
     >>> import os
     >>> os.remove(digest._path)
 
-When the size of the digest mbox reaches the maximum size threshold, a digest
-is crafted and sent out.  This puts two messages in the virgin queue, an HTML
-digest and an RFC 1153 plain text digest.  The size threshold is in KB.
+When the size of the digest mailbox reaches the maximum size threshold, a
+marker message is placed into the digest runner's queue.  The digest is not
+actually crafted by the handler.
 
     >>> mlist.digest_size_threshold = 1
     >>> mlist.volume = 2
     >>> mlist.next_digest_number = 10
     >>> size = 0
-    >>> for msg in makemsg():
+    >>> for msg in message_factory:
     ...     process(mlist, msg, {})
     ...     size += len(str(msg))
-    ...     if size > mlist.digest_size_threshold * 1024:
+    ...     if size >= mlist.digest_size_threshold * 1024:
     ...         break
-    >>> sum(1 for mboxmsg in digest_mbox(mlist))
-    0
-    >>> len(switchboard.files)
-    2
-    >>> for filebase in switchboard.files:
-    ...     qmsg, qdata = switchboard.dequeue(filebase)
-    ...     switchboard.finish(filebase)
-    ...     if qmsg.is_multipart():
-    ...         mimemsg = qmsg
-    ...         mimedata = qdata
-    ...     else:
-    ...         rfc1153msg = qmsg
-    ...         rfc1153data = qdata
-    >>> print mimemsg.as_string()
-    Content-Type: multipart/mixed; boundary="..."
-    MIME-Version: 1.0
-    From: _xtest-request@example.com
-    Subject: XTest Digest, Vol 2, Issue 10
-    To: _xtest@example.com
-    Reply-To: _xtest@example.com
-    Date: ...
-    Message-ID: ...
-    <BLANKLINE>
-    --...
-    Content-Type: text/plain; charset="us-ascii"
-    MIME-Version: 1.0
-    Content-Transfer-Encoding: 7bit
-    Content-Description: XTest Digest, Vol 2, Issue 10
-    <BLANKLINE>
-    Send XTest mailing list submissions to
-        _xtest@example.com
-    <BLANKLINE>
-    To subscribe or unsubscribe via the World Wide Web, visit
-        http://lists.example.com/listinfo/_xtest@example.com
-    or, via email, send a message with subject or body 'help' to
-        _xtest-request@example.com
-    <BLANKLINE>
-    You can reach the person managing the list at
-        _xtest-owner@example.com
-    <BLANKLINE>
-    When replying, please edit your Subject line so it is more specific
-    than "Re: Contents of XTest digest..."
-    <BLANKLINE>
-    --...
-    Content-Type: text/plain; charset="us-ascii"
-    MIME-Version: 1.0
-    Content-Transfer-Encoding: 7bit
-    Content-Description: Today's Topics (8 messages)
-    <BLANKLINE>
-    Today's Topics:
-    <BLANKLINE>
-       1. Test message 1 (aperson@example.com)
-       2. Test message 2 (aperson@example.com)
-       3. Test message 3 (aperson@example.com)
-       4. Test message 4 (aperson@example.com)
-       5. Test message 5 (aperson@example.com)
-       6. Test message 6 (aperson@example.com)
-       7. Test message 7 (aperson@example.com)
-       8. Test message 8 (aperson@example.com)
-    <BLANKLINE>
-    --...
-    Content-Type: multipart/digest; boundary="..."
-    MIME-Version: 1.0
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 1
-    Message: 1
-    <BLANKLINE>
-    Here is message 1
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 2
-    Message: 2
-    <BLANKLINE>
-    Here is message 2
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 3
-    Message: 3
-    <BLANKLINE>
-    Here is message 3
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 4
-    Message: 4
-    <BLANKLINE>
-    Here is message 4
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 5
-    Message: 5
-    <BLANKLINE>
-    Here is message 5
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 6
-    Message: 6
-    <BLANKLINE>
-    Here is message 6
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 7
-    Message: 7
-    <BLANKLINE>
-    Here is message 7
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    From: aperson@example.com
-    To: _xtest@example.com
-    Subject: Test message 8
-    Message: 8
-    <BLANKLINE>
-    Here is message 8
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    --...
-    >>> dump_msgdata(mimedata)
-    _parsemsg: False
-    isdigest : True
-    listname : _xtest@example.com
-    recips   : set([])
-    version  : 3
-
-
-    >>> print rfc1153msg.as_string()
-    From: _xtest-request@example.com
-    Subject: XTest Digest, Vol 2, Issue 10
-    To: _xtest@example.com
-    Reply-To: _xtest@example.com
-    Date: ...
-    Message-ID: ...
-    MIME-Version: 1.0
-    Content-Type: text/plain; charset="us-ascii"
-    Content-Transfer-Encoding: 7bit
-    <BLANKLINE>
-    Send XTest mailing list submissions to
-        _xtest@example.com
-    <BLANKLINE>
-    To subscribe or unsubscribe via the World Wide Web, visit
-        http://lists.example.com/listinfo/_xtest@example.com
-    or, via email, send a message with subject or body 'help' to
-        _xtest-request@example.com
-    <BLANKLINE>
-    You can reach the person managing the list at
-        _xtest-owner@example.com
-    <BLANKLINE>
-    When replying, please edit your Subject line so it is more specific
-    than "Re: Contents of XTest digest..."
-    <BLANKLINE>
-    <BLANKLINE>
-    Today's Topics:
-    <BLANKLINE>
-       1. Test message 1 (aperson@example.com)
-       2. Test message 2 (aperson@example.com)
-       3. Test message 3 (aperson@example.com)
-       4. Test message 4 (aperson@example.com)
-       5. Test message 5 (aperson@example.com)
-       6. Test message 6 (aperson@example.com)
-       7. Test message 7 (aperson@example.com)
-       8. Test message 8 (aperson@example.com)
-    <BLANKLINE>
-    <BLANKLINE>
-    ----------------------------------------------------------------------
-    <BLANKLINE>
-    Message: 1
-    From: aperson@example.com
-    Subject: Test message 1
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 1
-    <BLANKLINE>
-    <BLANKLINE>
-    ------------------------------
-    <BLANKLINE>
-    Message: 2
-    From: aperson@example.com
-    Subject: Test message 2
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 2
-    <BLANKLINE>
-    <BLANKLINE>
-    ------------------------------
-    <BLANKLINE>
-    Message: 3
-    From: aperson@example.com
-    Subject: Test message 3
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 3
-    <BLANKLINE>
-    <BLANKLINE>
-    ------------------------------
-    <BLANKLINE>
-    Message: 4
-    From: aperson@example.com
-    Subject: Test message 4
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 4
-    <BLANKLINE>
-    <BLANKLINE>
-    ------------------------------
-    <BLANKLINE>
-    Message: 5
-    From: aperson@example.com
-    Subject: Test message 5
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 5
-    <BLANKLINE>
-    <BLANKLINE>
-    ------------------------------
-    <BLANKLINE>
-    Message: 6
-    From: aperson@example.com
-    Subject: Test message 6
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 6
-    <BLANKLINE>
-    <BLANKLINE>
-    ------------------------------
-    <BLANKLINE>
-    Message: 7
-    From: aperson@example.com
-    Subject: Test message 7
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 7
-    <BLANKLINE>
-    <BLANKLINE>
-    ------------------------------
-    <BLANKLINE>
-    Message: 8
-    From: aperson@example.com
-    Subject: Test message 8
-    To: _xtest@example.com
-    Message-ID: ...
-    <BLANKLINE>
-    Here is message 8
-    <BLANKLINE>
-    <BLANKLINE>
-    End of XTest Digest, Vol 2, Issue 10
-    ************************************
-    <BLANKLINE>
-    >>> dump_msgdata(rfc1153data)
-    _parsemsg: False
-    isdigest : True
-    listname : _xtest@example.com
-    recips   : set([])
-    version  : 3
-
-
-Internationalized digests
--------------------------
-
-When messages come in with a content-type character set different than that of
-the list's preferred language, recipients will get an internationalized
-digest.  French is not enabled by default site-wide, so enable that now.
-
-    >>> config.languages.enable_language('fr')
 
-    # Simulate the site administrator setting the default server language to
-    # French in the configuration file.  Without this, the English template
-    # will be found and the masthead won't be translated.
-    >>> config.push('french', """
-    ... [mailman]
-    ... default_language: fr
-    ... """)
+    >>> sum(1 for msg in digest_mbox(mlist))
+    0
+    >>> len(digest_queue.files)
+    1
 
-    >>> mlist.preferred_language = u'fr'
-    >>> msg = message_from_string("""\
-    ... From: aperson@example.org
-    ... To: _xtest@example.com
-    ... Subject: =?iso-2022-jp?b?GyRCMGxIVhsoQg==?=
-    ... MIME-Version: 1.0
-    ... Content-Type: text/plain; charset=iso-2022-jp
-    ... Content-Transfer-Encoding: 7bit
-    ...
-    ... \x1b$B0lHV\x1b(B
-    ... """)
+The digest has been moved to a unique file.
 
-Set the digest threshold to zero so that the digests will be sent immediately.
+    >>> from mailman.utilities.mailbox import Mailbox
+    >>> from mailman.testing.helpers import get_queue_messages
+    >>> item = get_queue_messages('digest')[0]
+    >>> for msg in Mailbox(item.msgdata['digest_path']):
+    ...     print msg['subject']
+    Test message 2
+    Test message 3
+    Test message 4
+    Test message 5
+    Test message 6
+    Test message 7
+    Test message 8
+    Test message 9
 
-    >>> mlist.digest_size_threshold = 0
-    >>> process(mlist, msg, {})
-    >>> sum(1 for mboxmsg in digest_mbox(mlist))
-    0
-    >>> len(switchboard.files)
-    2
-    >>> for filebase in switchboard.files:
-    ...     qmsg, qdata = switchboard.dequeue(filebase)
-    ...     switchboard.finish(filebase)
-    ...     if qmsg.is_multipart():
-    ...         mimemsg = qmsg
-    ...         mimedata = qdata
-    ...     else:
-    ...         rfc1153msg = qmsg
-    ...         rfc1153data = qdata
-    >>> print mimemsg.as_string()
-    Content-Type: multipart/mixed; boundary="..."
-    MIME-Version: 1.0
-    From: _xtest-request@example.com
-    Subject: Groupe XTest, Vol. 2, Parution 11
-    To: _xtest@example.com
-    Reply-To: _xtest@example.com
-    Date: ...
-    Message-ID: ...
-    <BLANKLINE>
-    --...
-    Content-Type: text/plain; charset="iso-8859-1"
-    MIME-Version: 1.0
-    Content-Transfer-Encoding: quoted-printable
-    Content-Description: Groupe XTest, Vol. 2, Parution 11
-    <BLANKLINE>
-    Envoyez vos messages pour la liste XTest =E0
-        _xtest@example.com
-    <BLANKLINE>
-    Pour vous (d=E9s)abonner par le web, consultez
-        http://lists.example.com/listinfo/_xtest@example.com
-    <BLANKLINE>
-    ou, par courriel, envoyez un message avec =AB=A0help=A0=BB dans le corps ou
-    dans le sujet =E0
-        _xtest-request@example.com
-    <BLANKLINE>
-    Vous pouvez contacter l'administrateur de la liste =E0 l'adresse
-        _xtest-owner@example.com
-    <BLANKLINE>
-    Si vous r=E9pondez, n'oubliez pas de changer l'objet du message afin
-    qu'il soit plus sp=E9cifique que =AB=A0Re: Contenu du groupe de XTest...=A0=
-    =BB
-    <BLANKLINE>
-    --...
-    Content-Type: text/plain; charset="utf-8"
-    MIME-Version: 1.0
-    Content-Transfer-Encoding: base64
-    Content-Description: Today's Topics (1 messages)
-    <BLANKLINE>
-    VGjDqG1lcyBkdSBqb3VyIDoKCiAgIDEuIOS4gOeVqiAoYXBlcnNvbkBleGFtcGxlLm9yZykK
-    <BLANKLINE>
-    --...
-    Content-Type: multipart/digest; boundary="..."
-    MIME-Version: 1.0
-    <BLANKLINE>
-    --...
-    Content-Type: message/rfc822
-    MIME-Version: 1.0
-    <BLANKLINE>
-    Content-Transfer-Encoding: 7bit
-    From: aperson@example.org
-    MIME-Version: 1.0
-    To: _xtest@example.com
-    Content-Type: text/plain; charset=iso-2022-jp
-    Subject: =?iso-2022-jp?b?GyRCMGxIVhsoQg==?=
-    Message: 1
-    <BLANKLINE>
-    一番
-    <BLANKLINE>
-    <BLANKLINE>
-    --...
-    --...
-    >>> dump_msgdata(mimedata)
-    _parsemsg: False
-    isdigest : True
-    listname : _xtest@example.com
-    recips   : set([])
-    version  : 3
-
-    >>> print rfc1153msg.as_string()
-    From: _xtest-request@example.com
-    Subject: Groupe XTest, Vol. 2, Parution 11
-    To: _xtest@example.com
-    Reply-To: _xtest@example.com
-    Date: ...
-    Message-ID: ...
-    MIME-Version: 1.0
-    Content-Type: text/plain; charset="utf-8"
-    Content-Transfer-Encoding: base64
-    <BLANKLINE>
-    ...
-    <BLANKLINE>
-    >>> dump_msgdata(rfc1153data)
-    _parsemsg: False
-    isdigest : True
-    listname : _xtest@example.com
-    recips   : set([])
-    version  : 3
+Digests are actually crafted and sent by a separate digest queue runner.
diff --git a/src/mailman/pipeline/to_digest.py b/src/mailman/pipeline/to_digest.py
index b85764ac9..ebb40a77c 100644
--- a/src/mailman/pipeline/to_digest.py
+++ b/src/mailman/pipeline/to_digest.py
@@ -15,15 +15,7 @@
 # You should have received a copy of the GNU General Public License along with
 # GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
 
-"""Add the message to the list's current digest and possibly send it."""
-
-# Messages are accumulated to a Unix mailbox compatible file containing all
-# the messages destined for the digest.  This file must be parsable by the
-# mailbox.UnixMailbox class (i.e. it must be ^From_ quoted).
-#
-# When the file reaches the size threshold, it is moved to the qfiles/digest
-# directory and the DigestRunner will craft the MIME, rfc1153, and
-# (eventually) URL-subject linked digests from the mbox.
+"""Add the message to the list's current digest."""
 
 from __future__ import absolute_import, unicode_literals
 
@@ -34,396 +26,16 @@ __all__ = [
 
 
 import os
-import re
-import copy
-import time
-import logging
+import datetime
 
-from StringIO import StringIO          # cStringIO can't handle unicode.
-from email.charset import Charset
-from email.generator import Generator
-from email.header import decode_header, make_header, Header
-from email.mime.base import MIMEBase
-from email.mime.message import MIMEMessage
-from email.mime.text import MIMEText
-from email.parser import Parser
-from email.utils import formatdate, getaddresses, make_msgid
 from zope.interface import implements
 
-from mailman import Message
-from mailman import Utils
-from mailman import i18n
-from mailman.Mailbox import Mailbox
-from mailman.Mailbox import Mailbox
+from mailman.Message import Message
 from mailman.config import config
-from mailman.core import errors
+from mailman.i18n import _
 from mailman.interfaces.handler import IHandler
-from mailman.interfaces.member import DeliveryMode, DeliveryStatus
-from mailman.pipeline.decorate import decorate
-from mailman.pipeline.scrubber import process as scrubber
-
-
-_ = i18n._
-
-UEMPTYSTRING = ''
-EMPTYSTRING = ''
-
-log = logging.getLogger('mailman.error')
-
-
-
-def process(mlist, msg, msgdata):
-    # Short circuit non-digestable lists.
-    if not mlist.digestable or msgdata.get('isdigest'):
-        return
-    mboxfile = os.path.join(mlist.data_path, 'digest.mbox')
-    mboxfp = open(mboxfile, 'a+')
-    mbox = Mailbox(mboxfp)
-    mbox.AppendMessage(msg)
-    # Calculate the current size of the accumulation file.  This will not tell
-    # us exactly how big the MIME, rfc1153, or any other generated digest
-    # message will be, but it's the most easily available metric to decide
-    # whether the size threshold has been reached.
-    mboxfp.flush()
-    size = os.path.getsize(mboxfile)
-    if size / 1024.0 >= mlist.digest_size_threshold:
-        # This is a bit of a kludge to get the mbox file moved to the digest
-        # queue directory.
-        try:
-            # Enclose in try/except here because a error in send_digest() can
-            # silently stop regular delivery.  Unsuccessful digest delivery
-            # should be tried again by cron and the site administrator will be
-            # notified of any error explicitly by the cron error message.
-            mboxfp.seek(0)
-            send_digests(mlist, mboxfp)
-            os.unlink(mboxfile)
-        except Exception, errmsg:
-            # Bare except is generally prohibited in Mailman, but we can't
-            # forecast what exceptions can occur here.
-            log.exception('send_digests() failed: %s', errmsg)
-    mboxfp.close()
-
-
-
-def send_digests(mlist, mboxfp):
-    # Set the digest volume and time
-    if mlist.digest_last_sent_at:
-        bump = False
-        # See if we should bump the digest volume number
-        timetup = time.localtime(mlist.digest_last_sent_at)
-        now = time.localtime(time.time())
-        freq = mlist.digest_volume_frequency
-        if freq == 0 and timetup[0] < now[0]:
-            # Yearly
-            bump = True
-        elif freq == 1 and timetup[1] <> now[1]:
-            # Monthly, but we take a cheap way to calculate this.  We assume
-            # that the clock isn't going to be reset backwards.
-            bump = True
-        elif freq == 2 and (timetup[1] % 4 <> now[1] % 4):
-            # Quarterly, same caveat
-            bump = True
-        elif freq == 3:
-            # Once again, take a cheap way of calculating this
-            weeknum_last = int(time.strftime('%W', timetup))
-            weeknum_now = int(time.strftime('%W', now))
-            if weeknum_now > weeknum_last or timetup[0] > now[0]:
-                bump = True
-        elif freq == 4 and timetup[7] <> now[7]:
-            # Daily
-            bump = True
-        if bump:
-            mlist.bump_digest_volume()
-    mlist.digest_last_sent_at = time.time()
-    # Wrapper around actually digest crafter to set up the language context
-    # properly.  All digests are translated to the list's preferred language.
-    with i18n.using_language(mlist.preferred_language):
-        send_i18n_digests(mlist, mboxfp)
-
-
-
-def send_i18n_digests(mlist, mboxfp):
-    mbox = Mailbox(mboxfp)
-    # Prepare common information (first lang/charset)
-    lang = mlist.preferred_language
-    lcset = Utils.GetCharSet(lang)
-    lcset_out = Charset(lcset).output_charset or lcset
-    # Common Information (contd)
-    realname = mlist.real_name
-    volume = mlist.volume
-    issue = mlist.next_digest_number
-    digestid = _('$realname Digest, Vol $volume, Issue $issue')
-    digestsubj = Header(digestid, lcset, header_name='Subject')
-    # Set things up for the MIME digest.  Only headers not added by
-    # CookHeaders need be added here.
-    # Date/Message-ID should be added here also.
-    mimemsg = Message.Message()
-    mimemsg['Content-Type'] = 'multipart/mixed'
-    mimemsg['MIME-Version'] = '1.0'
-    mimemsg['From'] = mlist.request_address
-    mimemsg['Subject'] = digestsubj
-    mimemsg['To'] = mlist.posting_address
-    mimemsg['Reply-To'] = mlist.posting_address
-    mimemsg['Date'] = formatdate(localtime=1)
-    mimemsg['Message-ID'] = make_msgid()
-    # Set things up for the rfc1153 digest
-    plainmsg = StringIO()
-    rfc1153msg = Message.Message()
-    rfc1153msg['From'] = mlist.request_address
-    rfc1153msg['Subject'] = digestsubj
-    rfc1153msg['To'] = mlist.posting_address
-    rfc1153msg['Reply-To'] = mlist.posting_address
-    rfc1153msg['Date'] = formatdate(localtime=1)
-    rfc1153msg['Message-ID'] = make_msgid()
-    separator70 = '-' * 70
-    separator30 = '-' * 30
-    # In the rfc1153 digest, the masthead contains the digest boilerplate plus
-    # any digest header.  In the MIME digests, the masthead and digest header
-    # are separate MIME subobjects.  In either case, it's the first thing in
-    # the digest, and we can calculate it now, so go ahead and add it now.
-    mastheadtxt = Utils.maketext(
-        'masthead.txt',
-        {'real_name' :        mlist.real_name,
-         'got_list_email':    mlist.posting_address,
-         'got_listinfo_url':  mlist.script_url('listinfo'),
-         'got_request_email': mlist.request_address,
-         'got_owner_email':   mlist.owner_address,
-         }, mlist=mlist)
-    # MIME
-    masthead = MIMEText(mastheadtxt.encode(lcset), _charset=lcset)
-    masthead['Content-Description'] = digestid
-    mimemsg.attach(masthead)
-    # RFC 1153
-    print >> plainmsg, mastheadtxt
-    print >> plainmsg
-    # Now add the optional digest header
-    if mlist.digest_header:
-        headertxt = decorate(mlist, mlist.digest_header, _('digest header'))
-        # MIME
-        header = MIMEText(headertxt.encode(lcset), _charset=lcset)
-        header['Content-Description'] = _('Digest Header')
-        mimemsg.attach(header)
-        # RFC 1153
-        print >> plainmsg, headertxt
-        print >> plainmsg
-    # Now we have to cruise through all the messages accumulated in the
-    # mailbox file.  We can't add these messages to the plainmsg and mimemsg
-    # yet, because we first have to calculate the table of contents
-    # (i.e. grok out all the Subjects).  Store the messages in a list until
-    # we're ready for them.
-    #
-    # Meanwhile prepare things for the table of contents
-    toc = StringIO()
-    print >> toc, _("Today's Topics:\n")
-    # Now cruise through all the messages in the mailbox of digest messages,
-    # building the MIME payload and core of the RFC 1153 digest.  We'll also
-    # accumulate Subject: headers and authors for the table-of-contents.
-    messages = []
-    msgcount = 0
-    msg = mbox.next()
-    while msg is not None:
-        if msg == '':
-            # It was an unparseable message
-            msg = mbox.next()
-            continue
-        msgcount += 1
-        messages.append(msg)
-        # Get the Subject header
-        msgsubj = msg.get('subject', _('(no subject)'))
-        subject = Utils.oneline(msgsubj, in_unicode=True)
-        # Don't include the redundant subject prefix in the toc
-        mo = re.match('(re:? *)?(%s)' % re.escape(mlist.subject_prefix),
-                      subject, re.IGNORECASE)
-        if mo:
-            subject = subject[:mo.start(2)] + subject[mo.end(2):]
-        username = ''
-        addresses = getaddresses([Utils.oneline(msg.get('from', ''),
-                                                in_unicode=True)])
-        # Take only the first author we find
-        if isinstance(addresses, list) and addresses:
-            username = addresses[0][0]
-            if not username:
-                username = addresses[0][1]
-        if username:
-            username = ' ({0})'.format(username)
-        # Put count and Wrap the toc subject line
-        wrapped = Utils.wrap('{0:2}. {1}'.format(msgcount, subject), 65)
-        slines = wrapped.split('\n')
-        # See if the user's name can fit on the last line
-        if len(slines[-1]) + len(username) > 70:
-            slines.append(username)
-        else:
-            slines[-1] += username
-        # Add this subject to the accumulating topics
-        first = True
-        for line in slines:
-            if first:
-                print >> toc, ' ', line
-                first = False
-            else:
-                print >> toc, '     ', line.lstrip()
-        # We do not want all the headers of the original message to leak
-        # through in the digest messages.  For this phase, we'll leave the
-        # same set of headers in both digests, i.e. those required in RFC 1153
-        # plus a couple of other useful ones.  We also need to reorder the
-        # headers according to RFC 1153.  Later, we'll strip out headers for
-        # for the specific MIME or plain digests.
-        keeper = {}
-        all_keepers = set(
-            header for header in
-            config.digests.mime_digest_keep_headers.split() +
-            config.digests.plain_digest_keep_headers.split())
-        for keep in all_keepers:
-            keeper[keep] = msg.get_all(keep, [])
-        # Now remove all unkempt headers :)
-        for header in msg.keys():
-            del msg[header]
-        # And add back the kept header in the RFC 1153 designated order
-        for keep in all_keepers:
-            for field in keeper[keep]:
-                msg[keep] = field
-        # And a bit of extra stuff
-        msg['Message'] = repr(msgcount)
-        # Get the next message in the digest mailbox
-        msg = mbox.next()
-    # Now we're finished with all the messages in the digest.  First do some
-    # sanity checking and then on to adding the toc.
-    if msgcount == 0:
-        # Why did we even get here?
-        return
-    toctext = toc.getvalue()
-    # MIME
-    try:
-        tocpart = MIMEText(toctext.encode(lcset), _charset=lcset)
-    except UnicodeError:
-        tocpart = MIMEText(toctext.encode('utf-8'), _charset='utf-8')
-    tocpart['Content-Description']= _("Today's Topics ($msgcount messages)")
-    mimemsg.attach(tocpart)
-    # RFC 1153
-    print >> plainmsg, toctext
-    print >> plainmsg
-    # For RFC 1153 digests, we now need the standard separator
-    print >> plainmsg, separator70
-    print >> plainmsg
-    # Now go through and add each message
-    mimedigest = MIMEBase('multipart', 'digest')
-    mimemsg.attach(mimedigest)
-    first = True
-    for msg in messages:
-        # MIME.  Make a copy of the message object since the rfc1153
-        # processing scrubs out attachments.
-        mimedigest.attach(MIMEMessage(copy.deepcopy(msg)))
-        # rfc1153
-        if first:
-            first = False
-        else:
-            print >> plainmsg, separator30
-            print >> plainmsg
-        # Use Mailman.pipeline.scrubber.process() to get plain text
-        try:
-            msg = scrubber(mlist, msg)
-        except errors.DiscardMessage:
-            print >> plainmsg, _('[Message discarded by content filter]')
-            continue
-        # Honor the default setting
-        for h in config.digests.plain_digest_keep_headers.split():
-            if msg[h]:
-                uh = Utils.wrap('{0}: {1}'.format(
-                    h, Utils.oneline(msg[h], in_unicode=True)))
-                uh = '\n\t'.join(uh.split('\n'))
-                print >> plainmsg, uh
-        print >> plainmsg
-        # If decoded payload is empty, this may be multipart message.
-        # -- just stringfy it.
-        payload = msg.get_payload(decode=True) \
-                  or msg.as_string().split('\n\n',1)[1]
-        mcset = msg.get_content_charset('us-ascii')
-        try:
-            payload = unicode(payload, mcset, 'replace')
-        except (LookupError, TypeError):
-            # unknown or empty charset
-            payload = unicode(payload, 'us-ascii', 'replace')
-        print >> plainmsg, payload
-        if not payload.endswith('\n'):
-            print >> plainmsg
-    # Now add the footer
-    if mlist.digest_footer:
-        footertxt = decorate(mlist, mlist.digest_footer)
-        # MIME
-        footer = MIMEText(footertxt.encode(lcset), _charset=lcset)
-        footer['Content-Description'] = _('Digest Footer')
-        mimemsg.attach(footer)
-        # RFC 1153
-        # BAW: This is not strictly conformant RFC 1153.  The trailer is only
-        # supposed to contain two lines, i.e. the "End of ... Digest" line and
-        # the row of asterisks.  If this screws up MUAs, the solution is to
-        # add the footer as the last message in the RFC 1153 digest.  I just
-        # hate the way that VM does that and I think it's confusing to users,
-        # so don't do it unless there's a clamor.
-        print >> plainmsg, separator30
-        print >> plainmsg
-        print >> plainmsg, footertxt
-        print >> plainmsg
-    # Do the last bit of stuff for each digest type
-    signoff = _('End of ') + digestid
-    # MIME
-    # BAW: This stuff is outside the normal MIME goo, and it's what the old
-    # MIME digester did.  No one seemed to complain, probably because you
-    # won't see it in an MUA that can't display the raw message.  We've never
-    # got complaints before, but if we do, just wax this.  It's primarily
-    # included for (marginally useful) backwards compatibility.
-    mimemsg.postamble = signoff
-    # rfc1153
-    print >> plainmsg, signoff
-    print >> plainmsg, '*' * len(signoff)
-    # Do our final bit of housekeeping, and then send each message to the
-    # outgoing queue for delivery.
-    mlist.next_digest_number += 1
-    virginq = config.switchboards['virgin']
-    # Calculate the recipients lists
-    plainrecips = set()
-    mimerecips = set()
-    # When someone turns off digest delivery, they will get one last digest to
-    # ensure that there will be no gaps in the messages they receive.
-    # Currently, this dictionary contains the email addresses of those folks
-    # who should get one last digest.  We need to find the corresponding
-    # IMember records.
-    digest_members = set(mlist.digest_members.members)
-    for address in mlist.one_last_digest:
-        member = mlist.digest_members.get_member(address)
-        if member:
-            digest_members.add(member)
-    for member in digest_members:
-        if member.delivery_status <> DeliveryStatus.enabled:
-            continue
-        # Send the digest to the case-preserved address of the digest members.
-        email_address = member.address.original_address
-        if member.delivery_mode == DeliveryMode.plaintext_digests:
-            plainrecips.add(email_address)
-        elif member.delivery_mode == DeliveryMode.mime_digests:
-            mimerecips.add(email_address)
-        else:
-            raise AssertionError(
-                'Digest member "{0}" unexpected delivery mode: {1}'.format(
-                    email_address, member.delivery_mode))
-    # Zap this since we're now delivering the last digest to these folks.
-    mlist.one_last_digest.clear()
-    # MIME
-    virginq.enqueue(mimemsg,
-                    recips=mimerecips,
-                    listname=mlist.fqdn_listname,
-                    isdigest=True)
-    # RFC 1153
-    # If the entire digest message can't be encoded by list charset, fall
-    # back to 'utf-8'.
-    try:
-        rfc1153msg.set_payload(plainmsg.getvalue().encode(lcset), lcset)
-    except UnicodeError:
-        rfc1153msg.set_payload(plainmsg.getvalue().encode('utf-8'), 'utf-8')
-    virginq.enqueue(rfc1153msg,
-                    recips=plainrecips,
-                    listname=mlist.fqdn_listname,
-                    isdigest=True)
+from mailman.interfaces.mailinglist import DigestFrequency
+from mailman.utilities.mailbox import Mailbox
 
 
 
@@ -437,4 +49,75 @@ class ToDigest:
 
     def process(self, mlist, msg, msgdata):
         """See `IHandler`."""
-        process(mlist, msg, msgdata)
+        # Short circuit for non-digestable messages.
+        if not mlist.digestable or msgdata.get('isdigest'):
+            return
+        # Open the mailbox that will be used to collect the current digest.
+        mailbox_path = os.path.join(mlist.data_path, 'digest.mmdf')
+        # Lock the mailbox and append the message.
+        with Mailbox(mailbox_path, create=True) as mbox:
+            mbox.add(msg)
+        # Calculate the current size of the mailbox file.  This will not tell
+        # us exactly how big the resulting MIME and rfc1153 digest will
+        # actually be, but it's the most easily available metric to decide
+        # whether the size threshold has been reached.
+        size = os.path.getsize(mailbox_path)
+        if size >= mlist.digest_size_threshold * 1024.0:
+            # The digest is ready to send.  Because we don't want to hold up
+            # this process with crafting the digest, we're going to move the
+            # digest file to a safe place, then craft a fake message for the
+            # DigestRunner as a trigger for it to build and send the digest.
+            mailbox_dest = os.path.join(
+                mlist.data_path,
+                'digest.{0.volume}.{0.next_digest_number}.mmdf'.format(mlist))
+            volume = mlist.volume
+            digest_number = mlist.next_digest_number
+            bump(mlist)
+            os.rename(mailbox_path, mailbox_dest)
+            config.switchboards['digest'].enqueue(
+                Message(),
+                listname=mlist.fqdn_listname,
+                digest_path=mailbox_dest,
+                volume=volume,
+                digest_number=digest_number)
+
+
+
+def bump(mlist):
+    """Bump the digest number and volume."""
+    now = datetime.datetime.now()
+    if mlist.digest_last_sent_at is None:
+        # There has been no previous digest.
+        bump = False
+    elif mlist.digest_volume_frequency == DigestFrequency.yearly:
+        bump = (now.year > mlist.digest_last_sent_at.year)
+    elif mlist.digest_volume_frequency == DigestFrequency.monthly:
+        # Monthly.
+        this_month = now.year * 100 + now.month
+        digest_month = (mlist.digest_last_sent_at.year * 100 +
+                        mlist.digest_last_sent_at.month)
+        bump = (this_month > digest_month)
+    elif mlist.digest_volume_frequency == DigestFrequency.quarterly:
+        # Quarterly.
+        this_quarter = now.year * 100 + (now.month - 1) // 4
+        digest_quarter = (mlist.digest_last_sent_at.year * 100 +
+                          (mlist.digest_last_sent_at.month - 1) // 4)
+        bump = (this_quarter > digest_quarter)
+    elif mlist.digest_volume_frequency == DigestFrequency.weekly:
+        this_week = now.year * 100 + now.isocalendar()[1]
+        digest_week = (mlist.digest_last_sent_at.year * 100 +
+                       mlist.digest_last_sent_at.isocalendar()[1])
+        bump = (this_week > digest_week)
+    elif mlist.digest_volume_frequency == DigestFrequency.daily:
+        bump = (now.toordinal() > mlist.digest_last_sent_at.toordinal())
+    else:
+        raise AssertionError(
+            'Bad DigestFrequency: {0}'.format(
+                mlist.digest_volume_frequency))
+    if bump:
+        mlist.volume += 1
+        mlist.next_digest_number = 1
+    else:
+        # Just bump the digest number.
+        mlist.next_digest_number += 1
+    mlist.digest_last_sent_at = now